>> that was a very powerful presentation, and i recall having a lump in my throat when i watched it. it was as if you were in the driver's seat watching your life come to an end in that split second. it was a very powerful videotape. in 1993, the amtrak railroad experienced the deadliest train crash in united states history. 47 passengers and crew were killed. 103 more were injured. the cause of the accident was unclear. the clues to this mystery were etched in twisted steel and buried in the mud of an alabama bayou, waiting for investigators to find them. amtrak's sunset limited is the

country's only remaining transcontinental train. >> sunset limited has an interesting history, it kind of dates back to the romantic time of train travel when it was very elegant and posh to travel by train. >> on september 20, 1993, trudy justin and her husband, larry, boarded the sunset limited in deming, new mexico, headed for florida. >> and i could sit there and look and talk to other people, but the best part is going to the dining car. we went to the dining car three times a day. and you just trot back there and they were really nice to you. >> after dinner, trudy and larry returned to their seats to rest. the train stopped briefly in new orleans to fix a broken air conditioner. by 2:30 a.m., it was running about 33 minutes behind schedule. it stopped in mobile, alabama, where the engineer waited until a freight train cleared the bridge up ahead.

then, the sunset limited started on the last leg of its trip, 750 miles to miami. the train throttled up to a cruising speed of 72 miles an hour, but visibility was hindered by fog. shortly before 3:00 a.m., the sunset limited approached the bayou canot bridge. in a matter of seconds, the train's three engines and next four cars plummeted into the water. the engine's fuel tanks ruptured, igniting the diesel fuel. >> then the people start yelling. we've got to get out of here because this is going to explode. >> the tugboat "mauvilla" was the first to report the accident. >> i believe we're right below the train. it's a hell of a fire in the middle of the river. where we're at, it's so foggy, i can't tell. i can't tell by looking at

radar, but there's something bad going on. >> it was a hell on earth kind of environment. it was just a horrific, horrific sight. >> the fire just was getting bigger. >> the "mauvilla" headed towards the flames, through the dense fog, to investigate. the crew pulled 17 passengers from the water. others were less fortunate. >> the parents of a little girl, she was 10 years old and handicapped. they pushed her to the arms of a rescuer through a window on their car and they didn't make it out. >> of the 220 passengers and crew onboard, 47 people were dead or unaccounted for. the fbi immediately flew to the crash site to investigate the possibility of terrorism. the coast guard and the national transportation safety board also sent investigators. >> the lead locomotive was found

buried in the mud at about a 45-degree angle, and three-quarters of it you could not see it. it just buried itself into the marsh. >> a second engine was alongside. a third was on the opposite side of the bridge. four derailed cars were nearby. as a local salvage crew began the grim task of pulling the dead from the bayou, investigators wanted to know what caused the deadliest accident in amtrak history.

in the early hours of september 22, 1993, amtrak's sunset limited plummeted off the bayou canot bridge in alabama, killing 42 passengers and 5 crew members. ten minutes before the sunset limited derailed, a freight train crossed the bridge in the opposite direction without incident. so, what happened in those ten minutes? divers recovered the train's event recorder from the bayou, which is like an airline's flight data recorder.

the tape revealed the train was traveling at 72 miles per hour and there was no brake application. whatever caused the crash, the engineer never saw it. investigators also discovered the signals on the track were green. >> the signals are controlled by a current that goes through the rail, and if the rail breaks, the signal will immediately turn red. so, the signal didn't turn red. >> the bridge was originally built in three sections. the southern section was a 165-foot steel truss bridge. the center section, a single 140-foot steel girder, was originally designed to pivot so river traffic could pass through. the northern section was simply 192 feet of track laid on top of a wooden trestle. the center section was totally

destroyed. despite its design, the swing feature of the bridge was never used, and investigators discovered it wasn't connected properly. >> since they never did use it as a swing bridge, they never did put in the same amount of tie-downs at the ends of the bridge to hold it in place. >> divers also examined the wood pilings that supported the bridge. >> we wanted to determine if the piles had undergone any kind of deterioration, such as damage from wood-destroying organisms like soft rot or brown rot decay. >> under a powerful microscope, scientists examined the cell walls of the samples. they looked for triangular-shaped microorganisms like these, which would indicate rot.

>> since we didn't find them present, then we were fairly comfortable that there was no appreciable deterioration of the piles contributing to the collapse. >> all that remained were three concrete piers. when investigators looked more closely, they discovered that the steel plates used to connect the bridge to the concrete were displaced 48 inches out of alignment. corley also examined the bolts that attached the metal plates to the concrete. >> those attachments were poorly maintained. in several cases, the holes that were supposed to have bolts through them didn't have anything recognizable in them. when we took the material out that was in those holes, we found that it was rust. >> when the sunset limited was pulled out of the water of bayou canot with sections of the bridge, it was evident that

something terrible had happened. investigators found that one of its sides, a metal girder, had been sheared off, as if struck on the end by a powerful force. corley measured the spacing of the girder's rivets and compared them to scratches along the side of the train's engine. >> the rivets made lines down the side of the engine, and you could match the lines made by those rivets with the bridge and confirm that that was what destroyed the girder on the bridge. >> but how did the train hit the outside of the bridge? while structural engineers examined all the evidence, coast guard investigators began interviewing eyewitnesses. what they were about to learn would provide a surprising lead to the investigation.

[ male announcer ] this is the cat that drank the milk... [ meows ] ...and let in the dog that woke the man who drove to the control room [ woman ] driverless mode engaged. find parking space. [ woman ] parking space found. [ male announcer ] ...that secured the data that directed the turbines that powered the farm that made the milk that went to the store that reminded the man to buy the milk that was poured by the girl who loved the cat. [ meows ] the internet of everything is changing everything. cisco. tomorrow starts here.

thetime to celebrateything ah, thwith your mates,mmer! grill a few dogs-- eh, hot dogs. bacon burgers... dachshund: "mattress discounters 4th of july sale ends soon"? bulldog: that cloud reminds me of... radio announcer: the tempur-pedic cloud collection. bulldog: that's it! radio announcer: now with 48 months interest-free financing-- basset hound: free financing? radio announcer: or get a queen size serta pillow top on sale for just $597. bulldog: that's a ringer of a deal! radio announcer: mattress discounters 4th of july sale ends soon. ♪ mattress discounters

investigators had many questions, but few answers to what caused the crash of amtrak's sunset limited. coast guard investigators also interviewed the men and women who helped in the rescue. >> my first thought was actually

to interview the crew of the tugboat "mauvilla," and that was because they were the reporting party of the accident. >> on the night of the crash, the "mauvilla" was making a routine run up the mobile river pushing a load of coal and pig iron. the "mauvilla" was pushing six barges, so the pilot was 400 feet away from the front of the barges. investigators learned that the pilot, willie odom, called the coast guard three hours before the train crash to report thick fog on the mobile river. about a half hour before the accident, odom said he steered his six barges around a bend in the mobile river and saw what appeared to be another tugboat on his radar. he said he steered towards it, hoping to tie onto it until visibility improved. but before that could happen, willie odom said his tugboat ran

aground. at this point, captain andrew stabler took over command of the "mauvilla" and called the coast guard, asking for help. >> we have a cable or something right into the wheel. the barges are floating adrift southbound. if anybody down there could help rounding them up, i would definitely appreciate it. >> around 2:50 a.m., the "mauvilla's" crew heard a crash, then saw a fire through the fog. >> i'm not sure what i'm seeing, but i'm seeing something that's burning. and it looks like it's crossways of the river. i ain't got out that far. if that's what i'm looking at, i don't have any idea. >> but if the "mauvilla" was on the mobile river, how were they able to see an accident on the bayou canot six miles away? >> mobile coast guard, we have got a mess up here. a train has run off the 14-mile railroad bridge.

>> but that was a mistake. the accident was on the bridge going across the bayou canot, a waterway that was closed to commercial boat traffic. >> bayou canot is a subsidiary of the mobile river. and in that very dense fog, operator of the tug mistakenly turned down into bayou canot, thinking it was a bend in the river a couple of miles further up river than where he really was. >> but how could this happen? investigators discovered that the "mauvilla" had no maps on board or even a compass. >> that's a very important thing, but the people on the river don't look at it that way. so what? all you do is steer between the banks and that's it. >> the "mauvilla" was equipped with radar, which wasn't required at the time, but the pilot, willie odom, wasn't trained to use it. when investigators heard odom's story, they went back to the bridge to examine what now

seemed like a key piece of evidence. >> the railroad bridge had a concrete pier that was holding up the bridge structure, and there was very fresh damage to the concrete of that bridge pier. >> something had hit the point of the pier. was it one of the "mauvilla's" barges? had the "mauvilla" caused the sunset limited to derail? >> when we found the left-hand barge, there was a similar mark of scraped paint and an indentation into the metal. in fact, it kind of looked t-shaped, which would indicate that the barge hit the top or flat portion as well as the edge of it, and it kind of gave it a little t-shaped mark. >> the other barges revealed more surprising clues. the center barge also had damage. there were vertical scrapes and an indentation.

a clue to the cause of the scrapes was found on the bridge's center span. >> when we pulled the girder out of the water, we did a visual inspection, and we noticed that some of the vertical steel members called stiffeners that were on the side of the girder had been bent flat against the girder. >> investigators measured the distance between the stiffeners and compared them to the vertical marks on the barge. they were a perfect match. now they had solid evidence to prove what caused the fatal crash of the sunset limited.

authorities knew that the tugboat "mauvilla" was in the vicinity of the bayou canot bridge shortly before the train crash and not on the mobile river, as the pilot thought. investigators discovered concrete chips on the "mauvilla's" front-left barge. the chips, along with samples from the bridge's pier, were sent to the fbi for analysis. >> each mix of concrete is unique. it has a specific amount of rocks, sand, cement, and water.

>> the investigators cut the concrete samples into razor-thin slices, then studied them under a transmitter-like microscope. the microscope shines polarized light through the samples, revealing the specific optical properties of the rocks, sand and cement. >> the fbi, after they examined the samples they found on the barge, determined that the concrete on the barge was the same as that found in the pier at the south end of the bridge. >> based on all the evidence, the national transportation safety board concluded that willie odom had gotten lost in the heavy fog as he piloted the "mauvilla" up the mobile river. with no maps or compass onboard, odom wasn't trained to read the boat's radar. he mistakenly veered left onto

the bayou canot instead of continuing up the mobile river. odom then mistook the radar image of the bridge for another tow barge. as he tried to maneuver towards it, his front-left barge struck the concrete south pier. the other two barges struck the bridge itself, knocking the bridge and the train track 48 inches out of alignment. when odom struck the bridge, he didn't know it, in part because he couldn't see the bridge through the fog, since it was unlighted. odom mistakenly believed he had run aground. inexplicably, the collision bent the track in an "s" shape, but didn't break it, which explains why the electrical current running through the tracks didn't break, either. >> had the track been severed, sure, that signal would have gone off down the line and there would have been a warning in

mobile that something was wrong on the track over bayou canot. >> coast guard records show the "mauvilla" struck the bridge only eight minutes before the sunset limited arrived. as the engineer headed towards the bridge, he saw a green light telling him the track ahead was all clear. >> as the train approached, i believe that the engine derailed just as it was getting to the portion of the bridge that had been moved sideways, and it hit that portion of the bridge, dragging the entire bridge along with the engines and destroying it. >> it's a big piece of steel out on the bridge, and the train struck it at 72 miles an hour. and then from that, you can tell it just tore the hell out of it. >> as the track collapsed, the lead engine and the next four cars flew into the water. some of the passenger cars stopped on the bridge, or the

fatality count might have been higher. tragically, the train was running about a half hour late due to the stop to repair the air conditioning. had the train been on time, it would have crossed the bridge before the "mauvilla" ran into it. >> i think this investigation just confirmed for me a couple of longstanding philosophies that i've had. one is that every accident is kind of a chain reaction. there is five or six links in the chain that all have to happen in order for an accident to happen. >> they never did put in the same amount of tie-downs at the ends of the bridge to hold it in place. therefore, it wasn't as resistant to a barge hitting it as it would have been if they had tied it down at the ends better. >> a year after the accident,

survivors gathered to remember those who lost their lives. by then, new regulations were in place to prevent similar accidents. tugboats are now required to have radar on board, and all operators are required to have formal training in how to use it. the boats are also required to have a compass on board as well as the necessary maps and river charts. there is also a requirement for all bridges to have lighting, even those on waterways closed to commercial traffic. willie odom was cleared of any criminal charges, but he never again piloted a tugboat. >> i think my main interest in all of the jobs i get into is to determine what went wrong so that we can learn from the bad things that have happened in the past and do better in the future.

>> i can't prevent what's happened, but if i learn lessons from it and then make changes in rules, regulations and procedures, i've done a lot to prevent that next one from happening in a crowded london underground station, a small, routine fire erupts into a deadly inferno and kills 31 people. dozens more are injured. a team of forensic experts searches for clues to the cause of the blaze and finds that the fire seemed to defy the very laws of physics. to unravel the cause of the mysterious fire, investigators would need to recreate a historic train station inside a modern computer. the sprawling london underground